When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I upgraded my 17" to 18" PFF7 on a MY03 WRX. I spoke to Mike Wood at Prodrive and he said to keep the pressures the same as for 17" - which is 34 front and 32 rear. But try doing a search on here - you might find people with better experiences.